At the beginning of your upkeep, target opponent reveals the top three cards of his or her library, may put a creature card from among them onto the battlefield, then puts the rest into his or her graveyard. You do the same with the top three cards of your library. If two creatures are put onto the battlefield this way, those creatures fight each other.

Guild Feud has one target: the opponent. You'll see what creature that player puts onto the battlefield before revealing the top three cards of your library and deciding whether to put a creature onto the battlefield yourself.

10/1/2012

If no creatures or only one creature is put onto the battlefield this way, no fight happens.

10/1/2012

Players can't cast spells or activate abilities between the creatures being put onto the battlefield and them fighting each other. Notably, you can't respond with a spell like Giant Growth.

10/1/2012

Any abilities that trigger when the two creatures enter the battlefield will be put on the stack after the fight, even if one or both creatures die.